The present invention relates to data storage devices. In particular, the present invention relates to positioning heads in data storage devices.
In data storage devices with movable heads, the position of the head is controlled using a servo control feedback loop. The control loop receives a reference signal that indicates the desired position for the recording head. This signal is combined with a position signal generated by the recording head that indicates the current position of the head to create a position error signal that indicates the distance between the desired position and the current position. Based on the position error signal, a controller in the loop issues control signals to one or more positioning units such as a voice coil motor (VCM) and microactuators to move the head toward the desired position.
Ideally, the servo loop would have complete control over the position of the head. However, in actual storage devices, the position of the head can be changed by other forces such as external forces applied to the data storage unit, and mechanical resonance in the structures that support the head.
To prevent off-track head motion caused by these forces, the prior art has suggested placing a sensor on a suspension assembly to sense motion of the suspension assembly relative to the end of an actuator arm. In particular, U.S. Pat. No. 5,862,015 shows a suspension sensor that detects strain in the suspension assembly caused by movement of the head relative to the actuator arm.
Although the prior art suggests that a sensor signal from a suspension sensor can be used to reduce off-track motion of the head, it does not describe the details of a control system that can perform this function. In particular, the patent provides no guidance as to how to build a control system that is able to filter head movement caused by external sources and resonance from head movement caused by an actuator.
Thus, a control system is needed that can be used to position a head based on information from a suspension sensor.
A method and data storage device are provided that reduce off-track motion due to resonant modes in the storage device. The off-track motion is reduced by sensing movement with a sensor located on a suspension assembly of the storage device. Based on this sensed movement, the sensor generates a signal that is used to drive a control system to minimize the off-track motion.
Additional features and benefits will become apparent upon a review of the following figures and their accompanying detailed description.